This invention [deals with molding of] is a mold assembly which, by way of example can mold relatively inextensible thin fiber reinforced plastic sheet material into box or container shaped products in a press in which the plastic sheet material reinforced such as by carbon or glass fibers has little or no stretchability. Usually molding of such boxlike products requires slightly outwardly inclined sidewalls to permit application of vertical pressure to the sidewall layers of material during heat cure. Usual molding of such boxlike products also involves use of metal molds having flared or outwardly inclined walls to permit separation of the product from both male and female mold parts. If the desired thin wall plastic boxlike product is to be made with precise right angular sides, problems arise in molding in that vertical pressure is not applicable to the sides and mold parts are not readily separable from the cured product.
According to the present invention, relatively thin high modulus fiber reinforced plastic sheet material can be molded in a press into boxlike products with precisely right angular sides or inwardly angled walls by use of slidably movable, sloping, metal mold wedges. The wedges are pushed downwardly by a press which cause them to slide in a lateral direction over stationary inclined surfaces of metal side guide blocks which guide the wedges at right angles to the pressure toward a male mold.
As indicated above the usual female mold with a male mold and die has flaring dimensional requirements to permit closure of the female mold die and removal of the product from about the male mold. Such flaring does not allow application of adequate pressure on the sides of the male mold. In the method and means herein disclosed, however, the female mold is replaced by one or more of what can be termed xe2x80x9cwedge molds.xe2x80x9d The xe2x80x9cwedge moldsxe2x80x9d are metal segments having one side matched in shape to a portion of the male mold to permit molding of a corresponding portion of product therebetween under heat and pressure. The other side of each wedge mold is inclined and arranged to be moved over a mated inclined surface of a stationary guide inclined downwardly toward the male mold. Each wedge mold is thereby moved transversely or laterally toward the male mold upon application of vertical pressure force against the top of the wedge mold.
A series of such stationary guides and associated wedge molds appropriately shaped and spaced about a male mold base can be pressurized from above by a press platen acting against a top plate mold section to cause plastic material placed on the male mold to be encompassed by wedge molds and cured under heat and pressure. In other words, each wedge mold is shaped on its mold side to match a side portion of the male mold while the other side has an inclined slide surface arranged to cause movement of the wedge mold over a cooperatively matching inclined surface of a stationary guide. The guide is positioned to direct movement of its respective wedge mold toward and in side pressure relation with material on the male mold upon application of vertical pressure on the wedge mold.
An object of the invention is to provide a method and means for molding relatively inextensible plastic sheet material with vertically applied press force which also translates into transverse molding force by way of a novel mold design incorporating wedge molds capable of making a wide range of difficult shapes.
In this regard a number of container shapes can be made using the invention such for example as with inwardly curved walls by using shaping wedges having curved surfaces designed to be pushed into mating curved surfaces of a male mold base. In such arrangements the male mold can also be in segments removable from the boxlike container product after its cured.
A feature of the invention is that both its method and means lend themselves to production of container products not only having straight sides but products having curved sidewalls or products with inwardly directed sidewalls using correspondingly shaped mold wedges which mate with matching surfaces on the male mold.
Other objects and structural features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, however, both in organization and the manner of construction, together with further objects and features thereof may be best understood by reference to the following description taken in connection with the accompanying drawings.